This invention relates to a mechanical plating process. More particularly, the invention relates to an improved mechanical plating process of the type in which a tenaciously adherent metallic coating is applied on a surface of an object by subjecting metal particles to mechanical energy in a liquid medium to flatten and cold weld the metal particles to the object surface to build up a continuous adherent metallic coating on the surface. Such mechanical plating processes are described in my earlier U.S. Pat. Nos. Re23,861; 2,689,808; 2,640,002; 3,023,127; 3,132,043; 3,479,209, which are herein incorporated by reference, and elsewhere.
The foregoing and other patents which followed, launched a whole new field of plating that was new and unique in that it used mechanical energy to build up the coating instead of thermal or electrical energy. Thus, the mechanical plating process is distinct from electroplating techniques, hot melt plating techniques (e.g. galvanizing) and the like and also from paints, such as zinc rich paints, in which metal particles are adhered to a substrate by means of a paint binder. Over the years, mechanical plating has grown, and commercial plants, numbering in the hundreds, are operating in various countries around the world. In current commercial operations, objects to be coated, plating metal, promoter chemicals and, optionally, impacting media (such as glass beads) are charged into multisided barrels which are rotated horizontally to produce coated objects by the tumbling mechanical action within the barrel. The coating, typically 0.00025 inches thick, is satisfactory in all respects. However, using optimum equipment and formulations, a processing time of at least about 30 minutes is ordinarily required. Moreover, barrel processing is inherently limited to the coating of objects small enough to fit within the rotating barrel. In general, therefore, barrel processing is limited to providing relatively thin coatings on relatively small objects and requires relatively long processing times.
It is an object of the present invention to provide an improved mechanical plating process. It is a further object to provide a mechanical plating process which can be used to provide relatively thick coatings, to provide coatings on large objects, and to provide coatings in a very short time.